1. Field of the Invention
This invention relates to a liquid mixing sensor which optically detects mixing ratio of a mixing liquid which includes at least two kinds of liquid components.
2. Description of Prior Art
In an internal engine of automobile, mixing fuel of gasoline and alcohol has been employed these days as a substitute of gasoline.
The substitute fuel forces to equip detector device which continuously detects mixing ratio of gasoline and alcohol to obtain an appropriate air-fuel ratio.
As seen in FIG. 5a, a counterpart detector device has an optically permeable member 720a, a bottom surface 722 of which is brought in contact with a mixing liquid 790 composed of gasoline and alcohol.
The member 702a is enclosed into a casing in which an epoxy mould resin 720 is filled to form an optically permeable column 702. A LED 704 and a photo diode 705 are embedded into the epoxy mould resin 720 in parallel relationship with the bottom surface 722.
Light beams from the LED 704 advance into an inner portion of the column 702 to be incident on the bottom surface 722 at more than a critical angle, and totally reflecting from the bottom surface 722 so as to impinge on the photo diode 705 which produces an output according to the intensity of the light beams impinged.
In this counterpart device, however, it is necessary to increase light receiving area of the photo diode due to increased incident angle on the column 702, and at the same time, it is necessary to determine greater distance between the photodiode 705 and the LED 704 so as to make scale of the device larger as a whole.
In addition, since it is necessary that the photo diode 705 and the LED 704 are each located in the mould resin 720, it is difficult to mould resin which has characteristics satisfactory for all the factors such as adhesion, expansion, refraction, transparency and endurance.
Therefore, it is an object of the invention to provide a detector device which last for long period of servicing time with low cost, small scale and high precision.
According to the invention, there is provided a mixing liquid ratio detector device comprising;
an optically permeable column, a bottom surface of which is brought in contact with a mixing liquid computerized of at least two components, and forming a boundary between the mixing liquid and the bottom surface which is brought in contact with a mixing liquid;
a light emitting element located to face to one side of the optically permeable column;
a light receiving element located in the opposite relationship with the light emitting element in a manner to face to another side of the column with the column interposed therebetween;
light receiving area of the light receiving element and light emitting area of the light emitting element being each arranged in the neighborhood of the column in generally perpendicular relationship with the boundary between the mixing liquid and the column, such that light beams from the light emitting element enter the boundary through one side of the column, the light beams incident on the boundary at an angle more than a critical angle being totally reflected from the boundary, and advancing through an inner portion of the column to come out from the other side of the column, and impinging on the light receiving element so as to produce an output according to the intensity of the light beams impinged thereon.
Further, another example of this kind of detector device (D) is shown in FIG. 5 as a kind of counterpart device.
This counterpart device carries a triangle prism 200 disposed to have a boundary with a mixing fuel 110. A LED (light emitting diode) 300 and a photo diode 400 are placed at both sides of the prism 200.
However, the detector device (D) has the following drawbacks.
The triangle prism is costly with insufficient compensation which is required due to temperature and deterioration of the LED, thus leading to avoiding high precision measurement.
Even recently introduced detector device has following drawbacks.
The height of optical permeable column increases to make difficult to be light weight. Light receiving area of the photo diode increases because broad range is required in which the light beams impinge on the photo diode.
Therefore, the invention has its object to provide a mixing liquid ratio detector device which is capable of eliminating all the drawbacks mentioned above, enabling to provide a mixing liquid ratio detector device which enables to accurately detect mixing ratio with lightweight column and small-scaled light receiving element because light receiving and light emitting diode are integrated by a gel-like filler.
According to the invention there is provided a liquid mixing ratio detector device comprising;
an optically permeable column, a bottom surface of which is brought in contact with a mixing liquid composed of at least two components, and forming a boundary between the mixing liquid and the bottom surface which is brought in contact with the mixing liquid;
a holder disposed for supporting the optically permeable column;
a light emitting element located to face to one side of the optically permeable column;
a light receiving element located in the opposite side to the light emitting element with the column interposed therebetween;
a transparent liquid filler disposed to fill between the light emitting element and the column, and at the same time, filling between the light receiving element and the column;
an arrangement between height and diametrical dimension of the column, and vertical position of the light receiving element being determined such that light beams from the light emitting element enter into one side of the column through the transparent liquid filler to be incident on the boundary, the light beams totally reflect from the boundary advance through inner portion of the column to come out partly from the other side of the column, and partly coming out from an upper surface of the column to impinge on the light receiving element so as to produce an output according to the light beams impinged.
It becomes unnecessary to make all the light beams from the boundary come out from the other side of the column, thus enabling to reduce axial dimension of the column.
On the other hand, the transparent liquid filler is determined to be smaller than the column in refraction index, thus controlling dispersion of the light beams which impinge on the light receiving element.
It is because of preventing the light beams from reflecting at the upper surface of the column that all the light beams incident on the boundary at more than a critical angle are adapted to come out from the other side of the column.